Fusible link



Dec. 6, 1949 J, M, JOHNSON 2,490,359

FUSIBLE LINK Filed Aug. 26, 1946 1 N VEN TOR. JQ/m M da/7.50

ATTO NEY.

Patented Dec. 6, 1949 WUSIBLE Jahn Malnhnson, J thnsoniCduntyaKans.

Application August 26, IMBSGHKNUWBSIIY 1 claim. (crise- 42) The present invention relates to fusible links of the type employed in fire fighting and alarm systems, and has for its general object the provision cf a fusible link of improved reliability which is more compact than heretofore, heater in appearance, and easier and more economical to manufacture.

Fusible links ordinarily are employed to join two halves of a metallic line which is under tension so that fusion of the link, by permitting the halves of the line to separate, will initiate the operation of mechanism for closing fire doors, turning on sprinkler systems, sounding local or remote alarms, or the like. In the past such links have taken the form of two fiat metallic plates bonded face to face by a fusible alloy, the individual plates having eyelets by means of which each may be connected to its respective half of the line. The resultant structure is unattractive in appearance and invites meddling which frequently results in faulty operation of a system; moreover, the type of construction employed lends itself to variation in the thickness of the fusible alloy between the plates with consequent lack of uniformity in the operation of the devices.

Broadly speaking, it is the object of the present invention to provide a fusible link which overcomes these difficulties.

One feature of the invention lies in the provision of a construction which obviates the fiat plates formerly used, and permits the ends of two wires to be linked by fusible material.

Another feature resides in the novel shape of the wires at their connected ends.

Another feature resides in the provision of a shell around the connected ends of the two Wires which controis the amount of fusible material surrounding,r them and discourages meddling with the link.

Other objects and features will appear in the course of the following description of the invention.

In the accompanying drawings which form a part of the specification and are to be read in conjunction therewith, and in which like reference numerals are employed to indicate like parts in the various views,

Fig. 1 is a side elevation of my fusible link,

Fig. 2 is a longitudinal cross section of the link,

Fig. 3 is an exploded perspective view of the various elements of the link, and

Fig. 4 is a sectional view drawn to an enlarged 2 scale taken along the line 4--4 of Fig. 2 in the direction of the arrows.

Referring more particularly to the drawings, the outer shell of my fusible link comprises a slotted sleeve lll. This is made of metal or other material having good heat conducting characteristics and can be formed easily and economically by bending a flat rectangle of the material around a cylindrical die until the opposite edges are approximately in abutting relationship. Extending into this sleeve from opposite directions are two elongated wires Il and l2. The ends of the wires within the sleeve are crimped at I3 and I4 in such a way that the undulations in each wire lie in a single plane (i. e., the plane of the paper, referring to Fig. 2). This permits the end portions of the two wires to be nested together within the sleeve as shown in Fig. 2, after which they are secured in place by a material l5 having comparatively low melting point.

The character of the system in which the fusible link is employed forms no part of the present invention, but it should be understood that the link is placed under tension by means of outwardly directed forces applied to the wires Il and l2. At ordinary atmospheric temperatures the material I5 remains solid and, notwithstanding the relatively small area of contact between this material and the wires H and I2, it will, due to the crimped and nested construction of the wires, prevent the Wires from pulling apart a's a result of the tension. When the temperature oi' the ambient air rises above the melting point of the material, however, this no long/er is true; the fusible material then releases the wires whereupon they immediateIyL'Separate due to the tension on the link initiating the operation of mechanism for closing nre doors, turning on fire extinguishers, and the like. If desired, a normally closed electrical circuit may be set up over the link so that the separation of the wires Il and I2 will open the circuit and through appropriate electrical relays operate analarm or other remote device.

Preferably, the wires Il'and I2 will be long enough to reach directly to the associated parts of the protective mechanism without any intervening wires, cable, or chain connections. The link is simple and near in appearance and, being entirely enclosed, does not invite meddling.

"It also is uniform' and .accurate in operation since the amount'of fusible material around the wires is regulated by theA sleeve.

From the foregoing it' will be'seen that this invention is one well adapted to attain all o! the ends and objects hereinbefore set forth together with other advantages which are obvious and which are inherent to the device.

It will be understood that certain features and subcombinations are of utility and may be employed Without reference to other features and subcombinations. This is contemplated by and is within the scope of the claim.

Inasmuch as many possible embodiments of the invention may be made without departing from the scope thereof, it is to be understood that all matter herein set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.

Having thus described my invention, I claim:

A fusible link comprising a body of fusible material, a pair of wires extending into said body from opposite sides thereof and having their ends embedded in the body, the embedded end of each Wire being sinuous in form, and the undulations in one Wire being nested with the undulations in the other, said undulations of both wires coplaner in a plane parallel to the axes of the wires.

JOHN M. JOHNSON.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS 

